一个基于Java Socket协议之上文件传输的完整示例，基于TCP通信完成。
除了基于TCP的二进制文件传输，还演示了JAVA Swing的一些编程技巧，Demo程序
实现主要功能有以下几点：
首先来看一下整个Dome的Class之间的关系图：
下面按照上图来详细解释各个类的功能与代码实现：
服务器端：
FileTransferServer类的功能首先是在端口9999创建一个服务器套接字并
开始监听连接。相关代码如下：
private void startServer(int port) { try { serverSocket = new ServerSocket(port); System.out.println("Server started at port :" + port); while(true) { Socket client = serverSocket.accept(); // blocked & waiting for income socket System.out.println("Just connected to " + client.getRemoteSocketAddress()); FileReceiveTask task = new FileReceiveTask(client); bar.setValue(0); // reset it now task.addPropertyChangeListener(new PropertyChangeListener() { public void propertyChange(PropertyChangeEvent evt) { if ("progress".equals(evt.getPropertyName())) { bar.setValue((Integer) evt.getNewValue()); } } }); task.execute(); } } catch (IOException e) { e.printStackTrace(); } } 关于PropertyChangeListener, Java提供了一个非常有力的工具类来
监控任意Bean Model的数据改变，程序通过添加该监听器实现对
SwingWorker的progress属性值改变的事件捕获，然后更新JProgressBar
实例对象，实现了UI的刷新。FileTransferServer类的完整源代码如下：
package com.gloomyfish.socket.tutorial.filetransfer; import java.awt.BorderLayout; import java.awt.FlowLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.IOException; import java.net.ServerSocket; import java.net.Socket; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JProgressBar; public class FileTransferServer extends JFrame implements ActionListener { /** * */ public final static String START_SVR = "Start"; public final static String SHUT_DOWN_SVR = "Shut Down"; public final static String END_FLAG = "EOF"; private static final long serialVersionUID = 1L; private ServerSocket serverSocket; private JButton startBtn; private JProgressBar bar; public FileTransferServer() { super("File Server"); initComponent(); setupListener(); } private void setupListener() { startBtn.addActionListener(this); } private void initComponent() { startBtn = new JButton(START_SVR); JPanel progressPanel = new JPanel(); progressPanel.setLayout(new BoxLayout(progressPanel, BoxLayout.Y_AXIS)); bar = new JProgressBar(); bar.setMinimum(0); bar.setMaximum(100); progressPanel.add(bar); getContentPane().setLayout(new BorderLayout()); JPanel btnPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT)); btnPanel.add(startBtn); getContentPane().add(btnPanel, BorderLayout.SOUTH); getContentPane().add(progressPanel, BorderLayout.CENTER); } private void startServer(int port) { try { serverSocket = new ServerSocket(port); System.out.println("Server started at port :" + port); while(true) { Socket client = serverSocket.accept(); // blocked & waiting for income socket System.out.println("Just connected to " + client.getRemoteSocketAddress()); FileReceiveTask task = new FileReceiveTask(client); bar.setValue(0); // reset it now task.addPropertyChangeListener(new PropertyChangeListener() { public void propertyChange(PropertyChangeEvent evt) { if ("progress".equals(evt.getPropertyName())) { bar.setValue((Integer) evt.getNewValue()); } } }); task.execute(); } } catch (IOException e) { e.printStackTrace(); } } public void showSuccess() { bar.setValue(100); JOptionPane.showMessageDialog(this, "file received successfully!"); } @Override public void actionPerformed(ActionEvent e) { if(START_SVR.equals(e.getActionCommand())) { Thread startThread = new Thread(new Runnable() { public void run() { startServer(9999); } }); startThread.start(); startBtn.setEnabled(false); } else if(SHUT_DOWN_SVR.equals(e.getActionCommand())) { } else { // do nothing... } } public static void main(String[] args) { FileTransferServer server = new FileTransferServer(); server.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); server.setSize(400, 400); server.setResizable(false); server.setVisible(true); } } FileReceiveTask是服务器端的文件接受类：
首先从建立的TCP流中得到文件名与文件大小，然后开始接受文件内容字节
并写入创建的文件对象流中，最后验证文件大小与写入的字节流是否相等
最后发送一条消息到文件发送方，告诉对方文件传输完成，可以关闭TCP流。
该类的完整源代码如下：
package com.gloomyfish.socket.tutorial.filetransfer; import java.io.BufferedOutputStream; import java.io.BufferedWriter; import java.io.DataInputStream; import java.io.File; import java.io.FileOutputStream; import java.io.OutputStreamWriter; import java.net.Socket; import javax.swing.SwingWorker; public class FileReceiveTask extends SwingWorker<Integer, Object> { private Socket _mSocket; public FileReceiveTask(Socket client) { this._mSocket = client; } @Override protected Integer doInBackground() throws Exception { // get file meta information DataInputStream input = new DataInputStream(_mSocket.getInputStream()); String fileName = input.readUTF(); int fileLength = (int)input.readLong(); // number of total bytes File file = new File("C://Users//fish//Downloads" + File.separator + fileName); BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream(file)); System.out.println("Received File Name = " + fileName); System.out.println("Received File size = " + fileLength/1024 + "KB"); // start to receive the content of the file and write them byte[] content = new byte[2048]; int offset = 0; int numReadBytes = 0; while(offset < fileLength && (numReadBytes = input.read(content)) > 0) { output.write(content, 0, numReadBytes); float precent = 100.0f * ((float)offset)/((float)fileLength); setProgress((int)precent); offset += numReadBytes; } System.out.println("numReadBytes = " + numReadBytes); if(offset < fileLength) { numReadBytes = input.read(content); System.out.println("numReadBytes = " + numReadBytes); System.out.println("File content error at server side"); } else { System.out.println("File Receive Task has done correctly"); } setProgress(100); // tell client to close the socket now, we already receive the file successfully!! BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(_mSocket.getOutputStream())); bufferedWriter.write("DONE/r/n"); bufferedWriter.flush(); // close the file and socket output.close(); _mSocket.close(); return 100; } } 客户端：
FileTransferClient是客户端UI类，用来实现到服务端的连接，然后选择
要传输的文件(图片，PDF，Word文档等各种二进制文件)。如果没有
输入服务器信息，会弹出提示要求输入。端口已经指定为：9999
【send File】按钮会打开文件选择框，用户选择要传输文件以后，创建
FileTransferTask线程，并开始执行文件传送。客户端UI代码如下：
package com.gloomyfish.socket.tutorial.filetransfer; import java.awt.BorderLayout; import java.awt.FlowLayout; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.beans.PropertyChangeEvent; import java.beans.PropertyChangeListener; import java.io.File; import java.net.InetSocketAddress; import java.net.SocketAddress; import javax.swing.BorderFactory; import javax.swing.BoxLayout; import javax.swing.JButton; import javax.swing.JFileChooser; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JProgressBar; import javax.swing.JTextField; /** * 我一般写英文注释，偶尔我也会写中文注释，只是觉得写英文 * 注释跟代码比较统一，无他。 */ public class FileTransferClient extends JFrame implements ActionListener { /** * */ private static final long serialVersionUID = 1L; public final static String SEND_CMD = "Send File"; public final static int MINIMUM = 0; public final static int MAXIMUM = 100; // public final static String CONNECT_CMD = "Connect"; private JButton sendFileBtn; private JTextField serverField; private JTextField portField; private JProgressBar bar; public FileTransferClient() { super("File Transfer Client"); initComponents(); } private void initComponents() { getContentPane().setLayout(new BorderLayout()); JPanel progressPanel = new JPanel(); progressPanel.setLayout(new BoxLayout(progressPanel, BoxLayout.Y_AXIS)); bar = new JProgressBar(); progressPanel.add(bar); bar.setMinimum(MINIMUM); bar.setMaximum(MAXIMUM); JPanel serverSettingPanel = new JPanel(); serverSettingPanel.setLayout(new GridLayout(2,2,5,5)); serverSettingPanel.setBorder(BorderFactory.createTitledBorder("Server Setting")); serverField = new JTextField(); portField = new JTextField(); serverSettingPanel.add(new JLabel("Server IP/Host:")); serverSettingPanel.add(serverField); serverSettingPanel.add(new JLabel("Server Port:")); serverSettingPanel.add(portField); sendFileBtn = new JButton(SEND_CMD); JPanel btnPanel = new JPanel(); btnPanel.setLayout(new FlowLayout(FlowLayout.RIGHT)); btnPanel.add(sendFileBtn); getContentPane().add(serverSettingPanel, BorderLayout.NORTH); getContentPane().add(btnPanel, BorderLayout.SOUTH); getContentPane().add(progressPanel, BorderLayout.CENTER); sendFileBtn.addActionListener(this); } @Override public void actionPerformed(ActionEvent e) { String command = e.getActionCommand(); if(command.equals(SEND_CMD)) { if(checkNull()) { JOptionPane.showMessageDialog(this, "Please enter server host and port in order to set up the connection!"); return; } JFileChooser chooser = new JFileChooser(); int status = chooser.showOpenDialog(null); if (status == JFileChooser.APPROVE_OPTION) { File f = chooser.getSelectedFile(); SocketAddress address = new InetSocketAddress(getServer(), getPort()); FileTransferTask task = new FileTransferTask(f, address, this); bar.setValue(0); task.addPropertyChangeListener(new PropertyChangeListener() { public void propertyChange(PropertyChangeEvent evt) { if ("progress".equals(evt.getPropertyName())) { bar.setValue((Integer) evt.getNewValue()); } } }); task.execute(); // 异步task执行 } } else { // do nothing } } public void showSuccess() { bar.setValue(100); JOptionPane.showMessageDialog(this, "file send successfully!"); } public String getServer() { return serverField.getText().trim(); } public int getPort() { return Integer.parseInt(portField.getText().trim()); } /** * make sure the UI already have some correct input information here!!! * @return */ private boolean checkNull() { String serverName = serverField.getText(); String port = portField.getText(); if(serverName == null || serverName.length() == 0 || port == null || port.length() == 0) { return true; } try { Integer.parseInt(port); // try to parse it as server port number , validation code. } catch(NumberFormatException ne) { ne.printStackTrace(); return true; } return false; } public static void main(String[] args) { FileTransferClient client = new FileTransferClient(); client.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); client.setSize(400, 400); client.setResizable(false); // client.pack(); client.setVisible(true); } } FileTransferTask实现的功能主要有：
该类完全源代码如下：
package com.gloomyfish.socket.tutorial.filetransfer; import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.DataInputStream; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStreamReader; import java.net.Socket; import java.net.SocketAddress; import javax.swing.SwingWorker; public class FileTransferTask extends SwingWorker<Integer, Object> { private File selectedFile; private Socket mSocket; private SocketAddress address; private FileTransferClient parent; public FileTransferTask(File file, SocketAddress address, FileTransferClient owner /*, JProgressBar progress*/) { this.address = address; this.selectedFile = file; mSocket = new Socket(); this.parent = owner; } @Override protected Integer doInBackground() throws Exception { // Get the size of the file long length = selectedFile.length(); if (length > Integer.MAX_VALUE) { throw new IOException("Could not completely read file " + selectedFile.getName() + " as it is too long (" + length + " bytes, max supported " + Integer.MAX_VALUE + ")"); } mSocket.connect(address); // Create the byte array to hold the file data mSocket.setSoLinger(true, 60); DataOutputStream dout = new DataOutputStream(mSocket.getOutputStream()); // now we start to send the file meta info. dout.writeUTF(selectedFile.getName()); dout.writeLong(length); dout.flush(); // end comment FileDataPackage pData = new FileDataPackage(); DataInputStream is = new DataInputStream(new FileInputStream(selectedFile)); byte[] bytes = new byte[2048]; // Read in the bytes int offset = 0; int numRead = 0; int fsize = (int)length; while (offset < fsize && (numRead=is.read(bytes, 0, bytes.length)) >= 0) { pData.setData(bytes, numRead); dout.write(pData.getPackageData(), 0, pData.getPackageData().length); dout.flush(); offset += numRead; float precent = 100.0f * ((float)offset)/((float)fsize); setProgress((int)precent); } System.out.println("total send bytes = " + offset); // Ensure all the bytes have been read in if (offset < fsize) { throw new IOException("Could not completely transfer file " + selectedFile.getName()); } mSocket.shutdownOutput(); // receive the file transfer successfully message from connection BufferedInputStream streamReader = new BufferedInputStream(mSocket.getInputStream()); BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(streamReader)); String doneMsg = bufferedReader.readLine(); if("DONE".equals(doneMsg)) { parent.showSuccess(); } // Close the file input stream setProgress(100); // dout.close(); mSocket.close(); is.close(); System.out.println("close it now......"); return 100; } } 数据包类如下，不解释！
package com.gloomyfish.socket.tutorial.filetransfer; /** * this is very simple file transfer protocol over TCP socket */ public class FileDataPackage { private int dataLength; // 数据包中数据长度，两个字节 private byte[] databuff; // 数据包中数据，meici最大不超过2048字节 public final static byte[] EOF = new byte[]{'E', 'O','F'}; public FileDataPackage() { dataLength = 0; databuff = new byte[2048]; } public byte[] getPackageData() { byte[] pData = new byte[dataLength]; // end comment System.arraycopy(databuff, 0, pData, 0, dataLength); return pData; } public void setData(byte[] data, int bsize) { dataLength = bsize; for(int i=0; i<databuff.length; i++) { if(i<bsize) { databuff[i] = data[i]; } else { databuff[i] = ' '; } } } } 每次发送的最大字节数为2048个字节。程序最终运行效果如下(win7 + JDK6u30)：
以上就是本文的全部内容，希望对大家的学习有所帮助。